Referring to FIG. 1A and FIG. 1B, FIG. 1A and FIG. 1B shows a conventional variable inductor. The conventional variable inductor 1000 has a primary conductor 1100 and a secondary conductor 1200, a switch 1300 and a current source 1400. The secondary conductor 1200 forms a loop on the outside of the primary conductor 1100. The switch 1300 couples in series with the secondary conductor 1200 and is turned on or off to make the loop close or open. The inductance of the conventional variable inductor 1000 is varied by closing and opening the loop with the switch 1300. The current source 1400 is also coupled in series with the secondary conductor 1200 and used to control the current flow in the secondary conductor 1200 to either increase or decrease the inductance.
Referring to FIG. 2, FIG. 2 shows another one conventional variable inductor. The conventional variable inductor 2000 has a first conductor 2100, a second conductor 2200, a first switch 2300, a second switch 2400 and a third switch 2500. The first switch 2300, the second switch 2400 and the third switch 2500 are disposed on three current paths connected between the first conductor 2100 and the second conductor 2200, respectively. The inductance of the conventional variable inductor 2000 is varied by closing and opening the first switch 2300, the second switch 2400 and the third switch 2500.
The conventional variable inductor 1000 may have a limitedly adjustable inductance range and an insufficient inductance resolution. The conventional variable inductor 2000 may have a lower Q value, durability issues and bias concern.
Accordingly, it is imperative to provide a variable inductor and an integrated circuit using the variable inductor which can overcome the aforesaid drawbacks of the conventional variable inductors.